Electrocardiograph



ELECTRO- CARDIOGRAPH Filed Aug. 2.7, 1942 4 Sheets-Sheet l March 23, 1948 A, J, K-IZAUR ELECTRO-CARDIOGRAPH Filed Aug. 27, 1942 4 Sheets-Sheet 2 March 23 1948. A J, KIZAUR, 2,438,341

ELECTRO- CARDIOGRAPH Filed Aug. 27, 1942 4 SheecS-Sheetl 3 INVENTORJ' March 23, 1948. A. J. KIZAUR ELECTRO-CARDIOGRAPH lFiled Aug. 27, 1942 4 Sheets-Sheet 4 Patented Mar. 23, 1948 UNITED STATES PATENT FFICE 2,438,341 ELno'rnocAnmoGnArn Arthur J. Kizaur, Cicero, Ill., assignor to General Electric X-Ray Corporation, Chicago, Ill., a corporation of New York application August 27, i942, seriai No. 456,373

Claims. 1

The present invention relates in general to indicating and recording apparatus and lhas more particular reference to oscillographs, the invention pertaining speciiically to electro-cardiographic apparatus. n

Recording apparatus oi the character inentioned ordinarily comprises motor mechanism for reelincr a strip o' sensitive material at uniform speed past an exposure window and electrical equipment for converting the fluctuating impulse to be pictured to an oscillating beam of light and applying such beam to the strip of sensitive material in order to apply a graph on the strip and thereby picturize the fluctuating impulses to make a record oi the same. Y

rI he apparatus for creating the fluctuating light beam, particularly where minute iiuctuations are involved, is of exceedingly sensitive character and jars or other vibrations applied to the apparatus may be impressed as extraneousvibration of the light beam, thereby producing errors in the record on the sensitive iilm unless care is taken to prevent such unwanted vibration in the apparatus; and it is an important object of the present invention to minimizeV vibration in apparatus of the character mentioned. Y c H Another important object is to provide spring driven motor means for reeling a record strip in apparatus oi the character mentioned, and toprovide a frame or mounting for the motor means, which mounting forms an integral part of the framework on which other elements of the recording apparatus are supported; a still further object being to form the motor mount as a tubular member extending longitudinally and preferablyccentrally of the framework of the apparatus to thereby rigidify and strengthen the same and thereby avoid unwanted vibration in the recording apparatus when the same is in operation. c

Another important object is to provide an improved spring motor comprising a helical spring anchored at one end on the frame of the apparatus and supported and enclosed within a tubular motor housing, the other end of the spring being drivingly connected with a winding and driving gear which overlies and closes the other end of the tubular housing.

A still further important object resides in utilizing a segmental Geneva wheel escapement for limiting the turning movement of the Winding and driving gear in either direction to prevent over-tensioning of the spring by excessive winding and also for preventing the motor from operating after the spring has become unwound to the eXtent that the driving effect thereof is insulicient to maintain the driven winding apparatus in operation at a desired rate oi speed.

Still another important object is to provide means for establishing the iiuctuating iniiuence to be recorded as a uctuat-ing or oscillating black- 2 out zone within a field of light, said iield of light containing the blackout zone shifting therein being applied to the sensitive strip at the exposure window whereby all of said strip in said window is exposed to light except in the area thereof that is blacked out.

Another important object is to provide for entirely blacking out the beam applied to the record strip through the exposure window in order to form thereon a vertical line of Width corresponding Ato the blackout period, such line comprising the portion of the moving strip that is unexposed to light through the exposure Window during the blackout period; and such lines forming a time gauge on the record strip indicating a unit of elapsed time between adjacent lines.

Another important object is to provide means for impressing a speed indicating record on the recording strip as the same is drawn past the eX- posure window to show the place or places at which the rate of travel of the record strip changed, no matter how slightly; a further object being to utilize a blocking member movable in the exposure window preferably at an end thereof, said blocking member being movable in the window in response to the operation of a speed governor, the member being movable into the window from the edge thereof in proportion to the speed of movement oi the record strip as determined by the governor, thereby screening the edge portions of the record strip from light rays and producing an unexposed marginal portion in said strip, the thickness of which unexposed marginal portion varies with the speed of travel of the strip past the exposure Window.

Another important object is to produce a fluctuating blackout zone in a light beam by establishing the beam at a stationary light source and directing the beam past a stationary blocking rod so that the beam including the shadow of the blocking rod falls upon an oscillating mirror, thereby reflecting the shadow oi the rod as anv oscillating blacked out portion on the light beam.

Another important object is to periodically interrupt the light beam by rotating an interrupter wheel, preferably at uniiorm speed across the path of the beam, said interrupter wheel having outstanding blades or ngers adapted each to interrupt the light beam while lying in its path.

Another important object is to provide means for photographing identifying indicia upon the record strip; a further object, in this connection, being to utilize a card holder adapted to receive a typewritten or otherwise marked card in position to be illuminated and a light image thereof cast, as through a suitable lens, upon the sensitive record sheet to thus photograph the image of the written card on the record strip.

These and numerous other important objects and advantages, and inherent functions of the Fig. 2 is a rear side View of the apparatus shown Y in Fig. 1;

Fig. 3 is a sectional View illustrating a portion of the apparatus shown in Figs. 1 and 2;

Fig. 4 is a view of the structure shown in Fig. 3 seen from the right hand end thereof;

Fig. 5 is a perspective View of a lens and mirror system employed in the device shown in Figs. 1 and 2`;

Fig. 6 is a perspective view of means for recording identifying indicia on the record strip; and

Fig. '7 is a perspective view of speed indicating and recording apparatus.

To illustrate the invention, the drawings show indicating and recording apparatus H (Figs. 1 and 2) comprising an electrocardiograph embodying winding mechanism |3 for moving a record strip l5, at uniform speed, in the direction illustrated by arrows in Figs. 5, 6 and 7, behind a side wall |1 of a light-proof housing 35. The side wall l1 is formed with a window |9 through which the strip is progressively revealed for exposure.

Theside wall |1 also forms a part oi a framework 2| of exceedingly rigid construction and is preferably made of metal. Upon the side wall there is mounted operating and control mechanism for applying a beam of light, progressively modulated in accordance with the characteristics of an impulse t0 be recorded on the film. This mechanism is arranged to apply the light beam through the window I9 and upon the lm to thereby make a record of such impulse. Y The framework 2|, in the illustrated embodiment, includes a top panel 23 upon which some of the parts of the apparatus are mounted. In addition, the framework comprises bars 2%, rods 21, plates, 25, end panel 29, intermediate panels 26 and 39, and sheet metal bracing members 3|. All of these parts are interconnected as by welding Yor, other suitable fastening means including screws 33,'t0 form a rigid frame work for the support of the elements of the indicating and recording apparatus.

The frame work 2| embodies a housing 95 ci light proof construction within which the record strip is enclosed for exposure. Prior to exposure the unexposed record strip is supported on a storage reel 31 at one end of the housing 35, the record strip being progressively drawn from the reel 91 pastthe window 19 where it is exposed and thence around a hlm roller 99 at the opposite end of the housing 35. From the roller 39 the exposed film is delivered through a light proof slot in the housing 35 into a casing di containing a receiving reel for the exposed lm. The top of the casing d! is normally closed by a removable cover 43 to permit removal of the ex` posed record stripv for processing. The housing 35 opens at its top through the panel 23 and is normally closed by a light proof cover e5. A control knob i1 extends through the cover 115 and through manipulation of a rack and pinion, serves to operate a slide |9a on the wall l1 for the purpose of varying the width of the exposure window I9.

An indicator knob 49 may be drivingly connected with the roller 39 through a friction clutch.

This knob i9 may project upwardly of the cover 45, and said knob and cover may carry cooperating indicator means such as an index mark on the periphery of a flange portion'of the knob in position to sweep over or adjacent an indicating scale formed on the cover 95. The knob @9, because of its friction drive connection with the roller 39, may be adjusted for zeroizing purposes, in order to show the length of the record strip thatmay have passed the window during an exposure operation.

In order to draw the record strip at uniform speed past the window I9, the roller 39 is drivingly connected with ashaft 5| which extends downwardly thereof through the bottom of the housing 35. This shaft is suitably journaled, as at 53, on the frame work 2| and is provided with a pinion 55 making driving connection with a gear 51 on a shaft 59 which is also suitably journaled in the frame work 2|. The sha-ft 59, through a spring actuated clutch mechansm el, is drivingly connected with a pinion 63 which meshes with a gear 65. This gear, as shown in Figs. 3 and 4 of the drawings, is fastened on a shaft S1 journaled, as at 69, at its gear carrying end, in the panel 29 of the frame work, said panel being illustrated at the right hand end of Fig. l 0f the drawings. The other end of the shaft 91 is journaled, as at 1|, in a cover plate 85 mounted in the panel 99. The gear 6:11 is driven by a spring motor 13 comprising a tubular housing 15 which is connected at its ends to the panels 29 and 39 and to the intermediate panel 28 through which said tubular housing extends. The housing is rigidly fastened to each of the panels 'by means of outstanding lugs '11 formed thereon. Thus the housing of the motor 'constitutes an integral part of the frame work 42|, thereby utilizing the tubular housing as a longitudinally extending bracing member rigidifying the frame and making for an exceedingly sturdy structure.

Within the tubular housing 15, and loosely supported thereby, is a helical spring 19, one end of which is fastened, as at 8|, to the inner face of the gear 65 which is positioned across the open end of the tubular housing 'I5 and between said end and the panel 29. The other end of the spring 19 is fastened, as at 83, to the frame work but to a plate 95 which closes said end of the tubular housing, the plate being rigidly secured in the intermediate panel 39 of the frame work 2|. Y

In order to tension the spring 19 the panel 29 supports a pinion 81 tted with a stem 89 forming a dog clutch for the removable reception of and connection with a handle or crank 9|. The pinion 81 is in driving engagement with the gear 95, so that by turning the crank 9| the gear E55 may be caused to turn in a direction tensioning the spring 19. The gear 63 also is turned during the cranking operation, but slippage in the sprin-g clutch 6| prevents operation of the film driving mechanism.

In order to prevent undue tensioning of the spring 19, the shaft 61, outwardly of the panel 29, as shown in Figs. 3 and 4, is provided with a hub 93 carrying an eccentric pin 95 in position to engage successive slots 91 of a segmental Geneva wheel 99, the peripheral edges of which intermediate the slots 91 are curved, as at 19|, to ride upon the circular surface of the hub 93. The wheel 99Yis segmented or cut away on one side, along aline spaced from the axis of the wheel, whereby said wheel comprises a curved peimpulses, such as impulses developed by beam of light.

ripheralv edge portion inwhich the slots 9T and curved' portions 'IOI are `formed,'the said line ol segmentation Vdefining the opposite ends of said curved peripheral e'dgep'ortion of the' wheel. The said opposite ends ofthe curved peripheral edge portion of the segmental wheel '99' are unslotted 'toI` provide shoulders |53 to engage the pin 95 and prevent further turning movement of the shaft lwheneverthe springl'r'eaches a desired tension, either in being wound up 'or in being unwourid, when drivingthe recording apparatus.

The shaft I 'is directly connected withthe strip driving roller `3lA and carries a pulley I 05' which extends |beneath thebottombf the housing' 35. The pulley |95 kis connected by means of a belt |01 with a pulley |09 which extends beneath the bottom of the casing ll! and which is drivingly connected with the strip receiving reel in said casing. The intermediate portion ofv the frame work 2| carries galvanometer means lI (Fig. 1) supported rigidlyon one of the frame elements 3| at one sideof the frame work. This galvan'ometer comprises a reflecting mirror H3 (Fig. 5) mounted for oscillating movement about a horizontal axis. prises means for oscillating the mirror accurately in accordance with impulses appliedv on the gal- Vanometer. The en'dof the frame work 2|, remote from the winding'mechanism 3 supports electrical equipment I5; indicated in'Figs. l and 2, including an indicatingmeter Il', mounted on the panel 23, and suitable operating knobs IEB, for vcontrolling the equipmentv I5, which knobs are conveniently exposedupwardly. ofthe panel 23. The electrical equipment is yieldably supported on a sub-frame I I9 as on rubber supports |2| lsecured in one of the plates v23'iorming the frame Work. The apparatus also includes electrical'apparatus enclosed inY a box |23 which is supported inthe frame Work under the panel 23.

The electrical equipment is of a character adapted to transform and translate fluctuating heart action, and apply corresponding electrical impulses upon the galvanometer in order to vibrate or oscillate the mirror I I3 'in accordance with the impulses to be recorded.

The vibratory impulses thus imparted to the mirror ||3`are applied through the Window I9 (Fig. 5) upon the record ,strip l5 as the same is drawn past the window.. Immediately behind the window is disposed a suitable lens |25 for converging light passing through the window upon the record strip I5.

Light for application upon the record strip I5 originates at a`-source"comprislng a small incandescent lamp |21 enclosed in a housing |29 (Fig. 2) fixed in the frame work, preferably upon a longitudinal panel |3I which extends along one side of the spring motorhousing 'l5 and which is rigidly bolted thereto, said panel |3| carrying the driving mechanism 5I53. Light from the lamp |2`| is projected through lan opening |33 in the casing |29, and, as shown more clearly in Fig 5 of the drawings,v passes thence through a lens |35 carried in a lbracket |31, which also carries the lamp housing |29. Afterfpassing the lens |35, the light beamstrikes upon amirror |353 which is supported at a predetermined angle on one of the frame plates 25. From the mirror |39 the beam of light is reflected through a condensing lens 14| and directed'upon the mirror H3 of the galvanometer whence the light beam is reected asa verticallyvibrating or oscillating Part Vofv thisoscillating beam The galvanometer also com` strikes upon'a reflecting mirror |43 andis' reflected' thereby upon 'the' Wall 'at the 'window opening I9 thereof, so that a portion ofthe oscillating beam mayp'ass through' the opening I3 and through the lens |25 to impinge' upon the record stripl l5. Another'portion of the oscillating beam,`reected by the galvanometer rmirror i 'I 3, strikes another reiiecting mirror |45 which is positionedto direct that/'portion of the oscillating beam, impinging thereon, successively uponl two reflecting mirrors |41 and|fill'positioned'todirect the so relecte'd'beam portion upon the back of the ground glass screen |5|. This screen is mounted'in an opening formed inthepanel 23 so that avisual observation of the' beammaybe made from in front of the panel. y ,A

The mirrors I39, M|43, |55, M1 and |59 are mounted on suitablesupports'carried bythe frame plate 26, shownat the left handend of Fig. 3, which plate 26 is rigidlysupported ibyithe' housing ofthe motor 'I3 as by p'e'destalsV |53, ksotliat the mirror system is supporte'dentirely upon the rigid frame work of the motor.

The light beam which is appliedthrough the window i9 is'sufliciently'wide to extend'beyond the conines of the opening lg'thecentral'portions of the beam only'passing through vrthe opening and impingin'g upon therecrd"strip.l Consequently the record strip, which ypreferably 'comprises a light sensitive "film, will -be"en`tirely exposed to light except insuch'portionsthereof as are screened. Betweenthe 'window'opening'and the lm is placed a screenwhich may comprise a series of graduated marks |25a4 (Fig. 5) on' the back'of the lens |25,"which marks extend parallel with the direction ofmovement of thelm; These marks are equally spaced apart'and serve to throw' equidistant 'longitudinal shadows |55i'on the moving l'ilm to thereby prevent exposure of ie lm along such shadow lines""a,nd thus form a striated or lined appearance inthe 'exposed nlm after development "thereof, Suchlines forming gauge marks on the film for use in interpreting the record made thereon The record or'grap'his made onthe film' as a wavering line |51 `comprising'an unex'posed pci'- tion of the `film created"by"a'shadow"member, preferably comprising a wire j|59,"extending in the horizontal plane which 'includesthehorizontel axis of the galvanorneterinirror, saidshadowwire |55) being 'disposedbetweenithe'lamp YHifi andthe mirror 3, preferably between the reflecting mirror 39'and the condensing 'len'slill4 This wire is supported preferably on a bracket VIGI (Fig. 2) which also 'carries the reilecti'ng mirror-l 3'9" `and the condensing lensV |4I'. The 'wire' |559 vservesto black out the central portionspfthe lightV beam which is thus -reflectedfrom the'mi'rror I |-3 with a central blacked out portionin the 'oscillating beam which ultimately reaches'therecording-iilm i5' and the groundglass 5|. Accordingly,y the film |5 Will be exposed tolightraysyexcept in those portions of thelm-'whichffro'm'time totime extend in line with the blacked out portionof the light beam. The record graph-"lin'e|5'| consequently Will comprise unexpoised-"portions'of the nlm superimposedupon the shadowlines` |55.

In making graphical records, particularly records of heart action, itis of"ext'remeimpor tance to maintain constantv speed of travel of the record strip I5, in order that the diagnostician using the record strip for diagnostic-purposes may place reliance in the uniformity ofthe record so faras the'time elementr is coricerned, and means is provided Afor establishingi'time gauging lines |63 directly on the record strip. 'This is accomplished by means of a timing wheel |65 (Figs. 2 and 5) comprising a disc formed with peripheral fingers |51 extending radially outwardly of the edge of the disc. The disc is supported for rotation on a stem |59 which is journaled for rotation on a plate |1I which forms a part of the frame work 2|, being mounted on the panel |3I. The wheel is positioned for rotation so that the outstanding iingerssuccessively pass across the light beam emanating from the source |21, the wheel to this end being conveniently disposed between the lens |35 and the reecting mirror |39. The wheel |65 is turned at uniform speed corresponding with the speed of movement of the lm I by means of driving mechanism |13 powered by the motor 13 through the shaft 5I so that the light beam is blocked at equal intervals successively by the fingers |61 which preferably are equally spaced on the wheel. One of the blocking fingers of the wheel is preferably wider than the others in order to interrupt the light beam for a slightly longer interval. When the light beam is interrupted, of course no light whatever may fall upon the film I5 which therefore remains unexposed during such interval to create the transverse time gauge lines |53 thereon. Since in the illustrated embodiment there are four ngers |61 of uniform width and a wider finger |68, it will be noted that, every fifth time, the gauge line formed on the record strip I5 will be wider than the intervening four lines.

In order to drive the timing wheel |85, the shaft |69 thereof is provided With a gear |15 which in turn meshes with a gear train |11 supported on shafts carried by the plates I1I and |12 and the plate |3I, said gear train being driven by the shaft 5I. The gear train includes a governor |19, which operating in conjunction with a friction pad member ISI supported on the frame plate 38, serves to limit the speed at which the driving mechanism, and hence of the timing wheel |65, may be driven by the motor.

In spite of al1 precautions, it is exceedingly difficult to insure uniformity of speed of travel of the record strip I5 and of the timing wheel |65, and the present invention includes means for indicating on the record I5 any even slight varia- '.tions in speed. To this end a movable light block- ;ing member |83 (Figs. 2, 5 and '1) is provided `comprising a bar supported on a stem in front of :the lowermost end of the window opening I9. This stem is vertically movable in a supporting bearing |85 and is normally urged in an upward direction by means of a spring |81 encircling the stem and disposed between the bearing |85 and the block |83.. Beneath the bearing the stem is provided with a yoke |89 which receives an actuating nger ISI whereby the stem and the member |83 may be depressed downwardly in the bearing |85. The finger ISI is carried on a tilting frame |93 which is actuated by the stem |95 of a speed responsive device |81 (Figs. 2 and 5) of the ball governor type. The device |91 is drivingly connected with the gear train |11 and consequently rotates at a speed corresponding to the speed at which the said gear train is driven by the motor. As the device |81 is thus turned, the ball governor mechanism thereof serves to elevate the stem |95 in proportion toits speed, the stem rising and tilting the frame .|93 about its pivot |93 with increasing speed, thereby lowering the blocking member |83. When the mechanism is stationary the member |83 is at its highest elevation in the Window opening I9 and blocks the light ray at the bottom of the window to produce an unexposed film portion |89 (Figs. 5 and 7) at the edge of the lm, such portion being narrower when the device is operating at normal speed. Should any variation from normal speed occur during the operation of the device, the unexposed strip |99 will become wider if speed is decreased, and become narrower if speed increases. Any sudden change in speed will be shown as a shoulder 28| in the speed indicating area. Consequently the record itself will have at all times along an edge of the strip a clear indication of any variation in speed of the apparatus during the record making period.

It should be noted that the apparatus for making a record of speed variations, namely, the member ISS, the bearing support |85, and the device |91, are all supported on the rigid plate I'iI. Means is also provided for giving a visual indication of the speed at which the apparatus is operating at any instant during the making of a record, the same comprising a pointer 253 mounted on a stern 285 which in turn is pivotally supported in a bearing 251 (Fig. 2) carried by a bracket 259 on the plate ilI. The stem 255 has an actuating arm 2H and spring means 2| Id is provided for normally urging the stem in a direction to press the arm 2H against a stop provided by the bracket 259, the stem, when said arm 2|! engages the stop, being in position such that the pointer 253 is at a Zero speed indicating position on a dial 2I3 (Fig. 7) which dial is eX- posed through a window opening 2I5 (Figs. l and 2) defined by a suitable frame on the panel 23. The tilting frame |83 of the light blocking mernbei` |33 is provided with an arm 2 i1 which extends thence in position to engage the actuating arm ZII of the pointer device to press on said arm, as the speed of the device increases, to thereby turn the pointer device against the influence of its biasing spring 2| Ia so that the pointer 283 will move across the graduated scale 2 I3 as speed increases. The scale 2|3, preferably at its mid portion, may be provided with a normal speed indicating graduation to thereby show when the apparatus is operating at a predetermined normal operating speed.

rThe apparatus includes means operable, when the record strip I5 is stationary, as at the conclusion of a record making period, to apply identifying characters by photographing the same on the sensitive material which comprises the record strip I5. To this end the panel I1 is provided with a window opening 2I9 (Fig. 6) adjacent the recording window i5 and the panel 23 is provided with an opening defined by a frame 22| (Fig. i), which frame carries a hinged cover plate 223 normally pressed as by means of a spring toward closed position on the frame 22|. This cover 223 is formed to removably receive a data card on its upper side, upon which card may be formed the identifying indicia to 'be photographed upon the record strip I5. These characters may be conveniently applied to the card as by typewriting or other preferred marking process.

After the typed or otherwise marked card is positioned on the under side of the cover 323, the same may be closed on the frame 22| to expose the marked face of the card downwardly through the opening in the panel 23. Immediately beneath said opening an inclined mirror 225 is disposed in position to reflect an image of the card to and through the window opening 2 I 5 and upon an area of the strip I5, as indicated at 221. The projection of the image of the card from the mirror 225 through the window opening 2|9 may be accomplished either directly or by interposing a suitable lens 229 between the mirror and the opening 219, said lens 229 being supported in a bracket 23 I, which in turn may be mounted on the plate 25 which carries the mirrors 139, 143, I 45, lill and H49 and the lens |41.

At the moment when it is desired to photograph the image of the card upon the record strip I5, the card may be illuminated by energizing a lamp 233 which is disposed in a suitable housing 236 disposed beneath the panel 23 adjacent the mirror 225 and formed with an opening to direct light rays upon the supported indicia card on the under side of the cover member 223. The marked face of the card being thus illuminated, a light image thereof is formed on the record strip l in the area 221. Illumination of the lamp 233 may be controlled by means of a press button 235 disposed on the upper side of the panel 23 adjacent the frame 22|.

The apparatus and equipment herein disclosed affords an exceedingly lightweight recording device, due in part to the utilization of the housing of the motor 'l5 as a tubular, frame rigidifying backbone. By means of the manner in which the tubular housing of the motor 'l5 is disposed and anchored in the frame structure, an extremely lightweight frame with adequate rigidity is provided for the support of the driving mechanism. Furthermore, the arrangement of the driving mechanism snugly and along one side of the rigid motor housing makes for an exceedingly compact yet lightweight arrangement of the elements of the recording apparatus.

It is thought that the invention and its numerous attend-ant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the form herein disclosed being a preferred embodiment for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

l. In an electrocardiograph adapted to reproduce an oscillating beam of light upon a moving lm, a framework including a rigid tubular member and frame means on and outwardly of said tubular member, nlm carrying and moving means, and oscillating light beam producing means supported on said framework outwardly of said tubular member, motor means supported on said tubular member and drivingly connected with said lm moving means, said rigid tubular member forming a backbone for the framework and serving as the main support for the moving lm and the oscillating beam of light, whereby motor induced vibrations in the electrocardiograph are reduced to a minimum to thereby increase the accuracy of reproduction.

2. In an electrocardiograph mounted upon a framework and adapted to reproduce an oscillating beam of light upon a moving film driven from a spring motor, a tubular housing which forms a part of the framework of the electrocardiograph and which serves as a housing for the spring motor, a main winding and driving gear which overlies and closes one end of the tubular housing, and a helical spring supported and enclosed within the tubular housing, one end of the helical spring being anchored upon the framework of the electrocardiograph and the other end ybeing drivingly connected with the main winding and driving gear, said arrangement and construction of elements serving to reduce vibrations in the electrocardiograph to a minimum to thereby increase the accuracy of reproduction.

3. In an electrocardiograph adapted to reproduce an oscillating beam of light upon a moving nlm, light blocking means movable in one edge of said beam of light for variably blocking the same to prevent exposure of said moving lm, and means for moving said light blocking means into said beam of light in accordance with the speed of movement of the moving lm, whereby variations in the speed of the moving lm are indicated by a shadow of varying width upon the moving film.

4. In an electrocardiograph adapted to reproduce an oscillating beam of light upon a moving film, a light blocking member movable in an edge of said beam of light adapted to variably block a portion of the beam of light to prevent exposure of the moving film by said blocked portion of the beam, and speed responsive means driven in timed relation with the speed of said moving film and drivingly connected to move said blocking member progressively into said beam of light to increase the light blocking effect thereof in direct proportion to the speed at which said lm is moved, whereby increases in the speed of the lm are indicated by a shadow of increased width upon the moving film.

5. In an electrocardiograph adapted to reproduce an oscillating beam of light upon a moving film, mechanism for impressing a speed indicating record upon said moving film, said mechanism comprising speed responsive means driven in timed relation with the speed of the moving film, a movable light blocking member being adapted continuously to vblock out a portion of the beam of light whereby said blocked out portion is prevented from exposing the moving iilm, said light blocking member being subjected to motion in response to the variations in the speed of said speed responsive means, whereby changes in the speed of said moving nlm are indicated by changes in the width of an unexposed portion of said moving nlm.

ARTHUR J. KIZAUR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 406,678 Walker July 9, 1889 513,532 Richter Jan. 30, 1894 1,300,191 Pogue Apr. 8, 1919 1,591,612 Dickinson July 6, 1926 1,647,711 Nichols Nov. 1, 1927 1,791,207 Hindle Feb. 3, 1931 1,794,685 Hayman et al Mar. 3, 1931 2,038,021 Zand Apr. 21, 1936 2,047,983 Richards July 21, 1936 2,063,790 Carbonara Dec. 8, 1936 2,099,938 Lockhart Nov. 23, 1937 2,120,703 Janes June 14, 1938 2,230,502 Pearson Feb. 4, 1941 2,313,091 Renner Mar. 9, 1943 2,348,401 Manzanera May 9, 1944 

